This paper presents a fault-tolerant eXtended Generalized Fat Tree (XGFT) Network-On-Chip (NOC) implemented with a new fault-diagnosis-and-repair (FDAR) system. The FDAR system is able to locate faults and reconfigure switch nodes in such a way that the network can route packets correctly despite the faults. This paper presents how the FDAR finds the faults and reconfigures the switches. Simulation results are used for showing that faulty XGFTs could also achieve good performance, if the FDAR is used. This is possible if deterministic routing is used in faulty parts of the XGFTs and adaptive Turn-Back (TB) routing is used in faultless parts of the network for ensuring good performance and Quality-of-Service (QoS). The XGFT is also equipped with parity bit checks for detecting bit errors from the packets.